Friction transmission belt

ABSTRACT

In a frictional forced power transmission belt A whose back face is reinforced with a short fiber-containing rubber ( 12 ) into which short fibers oriented in a single direction are mixed, the short fiber-containing rubber ( 12 ) is provided integrally with the back face of the belt so that the direction of orientation of the short fibers forms an angle with respect to the widthwise direction of the belt.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 of International Patent ApplicationNo. PCT/JP03/12180, filed Sep. 24, 2003, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to frictional forced power transmissionbelts.

BACKGROUND ART

In automobiles, V-ribbed belts are widely used to drive accessories suchas fans, air conditioners, alternators and power steering.

Japanese Unexamined Patent Publication No. 10-9344 discloses a relatedV-ribbed belt in which a plain weave fabric made of cotton fibers andsynthetic fibers is stuck to the back face of the belt so that thecenter line of an angle between warp and weft yarns extends obliquelywith respect to the longitudinal direction of the belt withoutperforming any wide-angle process at all. This publication describesthat such an arrangement provides, without performing any wide-angleprocess on the back face fabric, the resistance of the belt tolongitudinal splits which is equivalent to that of the belt subjected toa wide-angle process.

Actually, implementation of a serpentine system for driving a pluralityof accessories by using a single frictional forced power transmissionbelt has been developed in recent years. Furthermore, in such aserpentine accessory drive system, a distance between pulleys has beennarrowed, and the span length of a belt between the pulleys has beenshortened due to the effect of a reduction in space for an engine room.

On the other hand, a serpentine accessory drive system generallyutilizes an auto-tensioner formed to allow a tensioner pulley to pressthe back face of a belt so that the tension of the belt is keptconstant. However, as shown in FIGS. 8A and 8B, in some cases, thereoccurs a so-called “belt deviation” in which side tracking of a belt Doccurs in the widthwise direction of the belt on a tensioner pulley 63that is a flat pulley provided between a pair of ribbed pulleys 61, 62.Then, if the span length of the belt is shortened as described above,this belt deviation increases an alignment angle formed by thebelt-running direction and the direction perpendicular to a pulley axis,thus causing the problem that noise is produced.

DISCLOSURE OF INVENTION

The present inventors found that factors lying outside a belt, such asdeviation in alignment of pulleys in front and in rear, deviation inalignment of a tensioner pulley, shape of each pulley and wobbling of abearing, are involved with factors lying within the belt, such as atendency of the belt to cause side tracking, which results in beltdeviation. Furthermore, the present inventors also found that amongthese factors, the deviation in alignment of a tensioner pulley iscaused by its inclination that occurs with the elapse of time, and thisdeviation is deeply involved with belt deviation.

An object of the present invention is to provide a frictional forcedpower transmission belt capable of correcting belt deviation caused byexternal factors.

In order to achieve the above object, the present invention allows thefrictional forced power transmission belt to have a tendency to causeside tracking in the widthwise direction of the belt so as to offsetbelt deviation resulting from external factors.

To be more specific, a frictional forced power transmission belt of thepresent invention is based on the premise that the back face of the beltis reinforced with a short fiber-containing rubber into which shortfibers oriented in a single direction are mixed. Furthermore, the beltis characterized in that the short fiber-containing rubber is providedintegrally with the back face of the belt so that the direction oforientation of the short fibers forms an angle with respect to thewidthwise direction of the belt.

According to the above-described embodiment, the belt has a tendency torun toward the direction of orientation of the short fibers in the shortfiber-containing rubber, and thus side tracking of the belt tends tooccur when the belt runs; therefore, the side tracking of the belt canoffset and correct the belt deviation caused by external factors.

In the present invention, the direction of orientation of the shortfibers in the short fiber-containing rubber preferably forms an angle ofnot less than 10° nor more than 45° with respect to the widthwisedirection of the belt. This is because such an embodiment caneffectively suppress belt deviation. That is, if this angle is smallerthan 10°, the effect of correcting belt deviation might be lessened, andif this angle is greater than 45°, the tendency of the belt itself tocause side tracking is increased such that the effect of correcting beltdeviation might be excessively heightened. From this viewpoint, asdescribed in the aftermentioned embodiments, this angle is morepreferably not less than 10° nor more than 30°.

Although an improvement in a cord embedded in the frictional forcedpower transmission belt can also forcibly provide the belt with atendency to cause side tracking, the strength and elongationcharacteristic of the belt, for example, are considerably affected ifthe number of twist for the cord is optimized. Furthermore, if thespiral pitches of the cord provided spirally within the belt areconstant, the spiral angle varies depending on the length of the belt;therefore, respective cord materials have to be prepared for variousbelts in order to provide each of the various belts with a certaintendency to cause side tracking, which increases the cost accordingly.To the contrary, according to the present invention, it is sufficient toprepare a single short fiber-containing rubber and to change the settingof the direction in which warp yarns in a cord fabric are extended, orthe direction of orientation of the short fibers in the shortfiber-containing unvulcanized rubber for each of the various belts, andtherefore, the necessity of preparation of respective materials as inthe improvement of the cord is obviated, thus suppressing a costincrease accordingly.

In the frictional forced power transmission belt of the presentinvention, a belt body may be a V-ribbed belt body.

The frictional forced power transmission belt of the present inventionis suitable to drive accessories of an automobile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique view of a V-ribbed belt A according to anembodiment of the present invention.

FIG. 2 is a diagram illustrating the layout of a serpentine accessorydrive system with the V-ribbed belt A according to the embodiment of thepresent invention wound around the system.

FIG. 3 is a diagram illustrating how the V-ribbed belt A according tothe embodiment of the present invention is wound around a pulley.

FIG. 4 is an oblique view of a V-ribbed belt B according to a referenceexample.

FIG. 5 is a diagram illustrating how the V-ribbed belt B according tothe reference example is wound around a pulley.

FIG. 6 is a diagram illustrating the layout of a tester for evaluatingbelt durability.

FIG. 7 is a graph showing the relationship between an angle that thedirection of orientation of short fibers forms with respect to thewidthwise direction of the belt, and belt deviation.

FIGS. 8A and 8B are diagrams each illustrating belt deviation thatoccurs in a V-ribbed belt on a tensioner pulley.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described indetail with reference to the drawings.

FIG. 1 illustrates a V-ribbed belt A according to the embodiment of thepresent invention.

This V-ribbed belt A whose belt body is formed by a V-ribbed belt bodyincludes: an adhesion rubber layer 1; a back face rubber layer 12provided integrally with the topside of the adhesion rubber layer 1,i.e., the back face of the belt; a rib rubber layer 3 providedintegrally with the backside of the adhesion rubber layer 1, i.e., aninner part of the belt; and a cord 4 embedded spirally in the center ofthe belt thickness direction of the adhesion rubber layer 1 so as toextend in an approximate belt longitudinal direction and at certainpitches in the belt widthwise direction.

The adhesion rubber layer 1 is formed into a plate band shape extendingin the belt longitudinal direction, and is made of a rubber compositionsuch as a chloroprene rubber (CR), an ethylene-propylene-diene monomer(EPDM) or a hydrogenated nitrile rubber (H-NBR). This adhesion rubberlayer 1 serves as a rubber layer that forms a portion of the belt bodyand holds the cord 4.

The back face rubber layer 12 is made of a rubber composition such as achloroprene rubber (CR), an ethylene-propylene-diene monomer (EPDM) or ahydrogenated nitrile rubber (H-NBR), and short fibers 12 a, 12 a, . . .such as nylon fibers and/or aramid fibers oriented in a single directionare mixed into the back face rubber layer 12. Further, the direction oforientation of the short fibers 12 a in this back face rubber layer 12forms an angle of not less than 10° nor more than 45° (preferably, anangle of not less than 10° nor more than 30°) with respect to the beltwidthwise direction. This back face rubber layer 12 contributes to powertransmission when the belt runs with the back face thereof wound arounda flat pulley.

The rib rubber layer 3 is made of a rubber composition such as achloroprene rubber (CR), an ethylene-propylene-diene monomer (EPDM) or ahydrogenated nitrile rubber (H-NBR) like the adhesion rubber layer 1,and short fibers 3 b, 3 b, . . . such as nylon fibers and/or aramidfibers oriented in the belt widthwise direction are mixed into the ribrubber layer 3 so as to improve the modulus of elasticity in the beltwidthwise direction. The rib rubber layer 3 at the inner part of thebelt is provided with protrusively formed six ribs 3 a, 3 a, . . . thatare extended in the belt longitudinal direction, and are provided atcertain pitches in the belt widthwise direction. This rib rubber layer 3plays the principal role in power transmission when the belt woundaround a ribbed pulley runs.

The cord 4 is formed of a twisted yarn that is made of polyethyleneterephthalate (PET) fibers, polyethylene naphthalate (PEN) fibers orpolyvinyl alcohol (PVA) fibers, for example, and that is subjected to anadhesion process using a resorcinol-formaldehyde-latex (RFL) solution orthe like and a process for drawing and heating the yarn prior to moldingof the belt. This cord 4 serves to impart strength and tensile strengthto the belt A.

The V-ribbed belt A can be fabricated by a known belt fabrication methodusing, instead of a fabric for reinforcing the back face of a belt, arubber sheet containing unvulcanized short fibers.

FIG. 2 illustrates the layout of pulleys used in a serpentine accessorydrive system for an automotive engine in which the V-ribbed belt A isprovided.

The layout of the pulleys used in the serpentine accessory drive systemincludes: a power steering pulley 21 located at an uppermost position;an AC generator pulley 22 located below the power steering pulley 21; atensioner pulley 23 located to the lower left of the power steeringpulley 21; a water pump pulley 24 located below the tensioner pulley 23;a crank shaft pulley 25 located to the lower left of the tensionerpulley 23; and an air conditioner pulley 26 located to the lower rightof the crank shaft pulley 25. Among these pulleys, those other than thetensioner pulley 23 and the water pump pulley 24, which are flatpulleys, are all ribbed pulleys. Further, the V-ribbed belt A is woundaround the power steering pulley 21 so that a ribbed part of the beltmakes contact therewith, and is then wound around the tensioner pulley23 so that the belt back face makes contact therewith. Thereafter, theV-ribbed belt A is sequentially wound around the crank shaft pulley 25and the air conditioner pulley 26 so that the ribbed part makes contacttherewith, is further wound around the water pump pulley 24 so that thebelt back face makes contact therewith, is then wound around the ACgenerator pulley 22 so that the ribbed part makes contact therewith, andis finally returns to the power steering pulley 21. Furthermore, asshown in FIG. 3, the V-ribbed belt A is wound around a pulley P so thatthe short fibers 12 a in the back face rubber layer 12 are oriented inthe direction inclined from an engine E toward the opposite side alongthe belt-running direction. This V-ribbed belt A is driven by the crankshaft pulley 25 so as to run in a clockwise direction, thus driving anaccessory pulley, e.g., the power steering pulley 21. Meanwhile, in thisautomotive engine, the alignment of the tensioner pulley 23 is deviateddue to its inclination that occurs with the elapse of time, thus causingdeviation of the V-ribbed belt A toward the engine as shown in FIG. 3.

The V-ribbed belt A formed as described above has a tendency to runtoward the direction of orientation of the short fibers 12 a in the backface rubber layer 12 when the belt A runs, and thus side tracking of thebelt A tends to occur when it runs. Therefore, the belt A is woundaround the pulleys 21 through 26 so that side tracking of the belt Aoccurs in the direction opposite to the direction in which beltdeviation occurs due to an external factor such as deviation inalignment of the tensioner pulley 23 as described above. Accordingly, itbecomes possible to offset and correct the belt deviation resulting fromthe external factor by utilizing the side tracking of the belt A, andthus it becomes possible to suppress the generation of noise.

Although an improvement in the cord 4 can also forcibly provide the beltA with a tendency to cause side tracking, the strength and elongationcharacteristic of the belt, for example, are considerably affected ifthe number of twist for the cord 4 is optimized. Furthermore, if thespiral pitches of the cord provided spirally within the belt areconstant, the spiral angle varies depending on the length of the belt;therefore, respective cord materials have to be prepared for variousbelts in order to provide each of the various belts with a certaintendency to cause side tracking, which increases the cost accordingly.To the contrary, if the belt is formed as described above, it issufficient to prepare a single unvulcanized back face rubber sheet andto change the setting of the direction of orientation of the shortfibers 12 a for each of the various belts, and therefore, the necessityof preparation of respective materials as in the improvement of the cord4 is obviated, thus suppressing a cost increase accordingly.

It should be noted that although the frictional forced powertransmission belt of the above-described embodiment has been describedas the V-ribbed belt A, the present invention is not limited to this inparticular, but may be applicable to other kinds of frictional forcedpower transmission belts such as V-belts.

REFERENCE EXAMPLE

FIG. 4 illustrates a V-ribbed belt B according to a reference example.It should be noted that the same components as those in the firstembodiment are identified by the same reference characters.

This V-ribbed belt B includes: an adhesion rubber layer 1; a back facereinforcement fabric 2 stuck to the topside of the adhesion rubber layer1, i.e., the belt back face, so as to be provided integrally therewith;a rib rubber layer 3 provided integrally with the backside of theadhesion rubber layer 1, i.e., an inner part of the belt; and a cord 4provided spirally in the center of the belt thickness direction of theadhesion rubber layer 1 so as to extend in an approximate beltlongitudinal direction and at certain pitches in the belt widthwisedirection.

The back face reinforcement fabric 2 is formed of a cord fabric that ismade of warp yarns 2 a and weft yarns 2 b such as nylon and/or cotton,and that is subjected to an adhesion process using a rubber cementobtained by dissolving rubber in a solvent. In the cord fabric, the warpyarns 2 a are relatively thick and the count thereof is high, while theweft yarns 2 b are relatively thin to a degree that the warp yarns 2 aare not disturbed and the count thereof is low. In addition, in the cordfabric constituting the back face reinforcement fabric 2, the direction,in which the warp yarns 2 a are extended, forms an angle of not lessthan 10° nor more than 45° with respect to the belt widthwise direction.This back face reinforcement fabric 2 contributes to power transmissionwhen the belt runs with the back face thereof wound around a flatpulley.

Other arrangements are similar to the aforementioned embodiment.

The V-ribbed belt B can be fabricated by a known belt fabricationmethod.

Further, if the V-ribbed belt B is wound around the pulleys in thelayout of the serpentine accessory drive system as shown in FIG. 2, theV-ribbed belt B is wound around a pulley P so that the warp yarns 2 a ofthe cord fabric in the back face reinforcement fabric 2 provided on thebelt back face are extended in the direction inclined from an engine Etoward the opposite side along the belt-running direction as shown inFIG. 5.

The V-ribbed belt B formed as described above has a tendency to runtoward the direction in which the warp yarns 2 a of the cord fabric areextended when the belt B runs, and thus side tracking of the belt Btends to occur when it runs. Therefore, the belt B is wound around thepulley so that the side tracking of the belt B occurs in the directionopposite to the direction in which belt deviation occurs due to anexternal factor such as deviation in alignment of the tensioner pulley.Accordingly, it becomes possible to offset and correct the beltdeviation resulting from the external factor by utilizing the sidetracking of the belt B, and thus it becomes possible to suppress thegeneration of noise.

Besides, since it is sufficient to prepare a single cord fabric and tochange the setting of the direction, in which the warp yarns 2 a of thecord fabric are extended, for each of various belts, the necessity ofpreparation of respective materials as in the improvement of the cord 4is obviated, and thus a cost increase can be suppressed accordingly.

Test and Evaluation

(Belt for Test and Evaluation)

As a belt for test and evaluation, the following exemplary V-ribbedbelts are prepared. In the following description, we consider an anglethat the direction, in which the bisector of belt-widthwise-directedangles between warp and weft yarns in a reinforcement fabric isextended, forms with respect to the belt widthwise direction, and anangle that the direction of orientation of short fibers forms withrespect to the belt widthwise direction. When the back face of the beltis viewed from the front, the bisector or the direction of orientationof the short fibers forms positive and negative angles incounterclockwise and clockwise directions with respect to the beltwidthwise direction, respectively.

Example 1

A V-ribbed belt according to Example 1 is provided at its back face witha plain weave reinforcement fabric so that an angle é that thedirection, in which the bisector of intersecting angles of warp and weftyarns orthogonal to each other is extended, forms with respect to thebelt widthwise direction is 0°, i.e., so that the direction of thebisector of the intersecting angles corresponds to the belt widthwisedirection. The V-ribbed belt according to Example 1 does not have atendency to cause side tracking in the belt widthwise direction. Itshould be noted that the number of ribs is three, and the length of thebelt is 900 mm.

Example 2

A V-ribbed belt according to Example 2 is formed in the same way as inExample 1, except the belt back face is provided with a plain weavereinforcement fabric so that an angle é that the direction, in which thebisector of intersecting angles of warp and weft yarns orthogonal toeach other is extended, forms with respect to the belt widthwisedirection is −10°. The V-ribbed belt according to Example 2 has atendency to cause side tracking in the direction of the bisector of theintersecting angles of the warp and weft yarns.

Example 3

A V-ribbed belt according to Example 3 is provided at its back face witha short fiber-containing back face rubber layer so that an angle é thatthe direction of orientation of short fibers forms with respect to thebelt widthwise direction is 0°, i.e., so that the direction oforientation of the short fibers corresponds to the belt widthwisedirection. The V-ribbed belt according to Example 3 does not have atendency to cause side tracking in the belt widthwise direction. Itshould be noted that the number of ribs is three, and the belt length is900 mm.

Example 4

A V-ribbed belt according to Example 4 is formed in the same way as inExample 3, except the belt back face is provided with a shortfiber-containing back face rubber layer so that an angle é that thedirection of orientation of short fibers forms with respect to the beltwidthwise direction is 10°. The V-ribbed belt according to Example 4 hasa tendency to cause side tracking in the direction of orientation of theshort fibers.

Example 5

A V-ribbed belt according to Example 5 is formed in the same way as inExample 3, except the belt back face is provided with a shortfiber-containing back face rubber layer so that an angle é that thedirection of orientation of short fibers forms with respect to the beltwidthwise direction is 2°. The V-ribbed belt according to Example 5 hasa tendency to cause side tracking in the direction of orientation of theshort fibers.

Example 6

A V-ribbed belt according to Example 6 is formed in the same way as inExample 3, except the belt back face is provided with a shortfiber-containing back face rubber layer so that an angle é that thedirection of orientation of short fibers forms with respect to the beltwidthwise direction is 30°. The V-ribbed belt according to Example 6 hasa tendency to cause side tracking in the direction of orientation of theshort fibers.

Example 7

A V-ribbed belt according to Example 7 is formed in the same way as inExample 3, except the belt back face is provided with a shortfiber-containing back face rubber layer so that an angle é that thedirection of orientation of short fibers forms with respect to the beltwidthwise direction is 40°. The V-ribbed belt according to Example 7 hasa tendency to cause side tracking in the direction of orientation of theshort fibers.

(Method for Test and Evaluation)

<Belt Deviation>

Belt deviation in a V-ribbed belt C according to each of Examples 1through 7 is tested and evaluated by using an automotive engine havingthe layout of the serpentine accessory drive system shown in FIG. 2. Inthis automotive engine, deviation in alignment of the tensioner pulley23 is caused by its inclination that occurs with the elapse of time,thus exerting an action that causes belt deviation toward the engine(i.e., toward the background of FIG. 2).

The V-ribbed belts C according to Examples 1 through 7 are each woundaround the pulleys 21 through 26 and allowed to run in a clockwisedirection so that belt deviation on the tensioner pulley 23 is measured.It should be noted that the belt deviation toward the engine (i.e.,toward the background of FIG. 2) is represented by “+”, and the beltdeviation toward the opposite direction (i.e., toward the foreground ofFIG. 2) is represented by “−”. In this method, the belt C according toExample 2 is wound around the pulleys so that the bisector of theintersecting angles of the warp and weft yarns in the back facereinforcement fabric extends in the direction inclined toward the enginealong the belt-running direction. On the other hand, as shown in FIG. 3,the belts C according to Examples 3 through 7 are each wound around thepulleys so that the direction of orientation of the short fibers in theback face rubber layer corresponds to the direction inclined from theengine E toward the opposite side along the belt-running direction.

<Durability of Belt>

The durability of each of the V-ribbed belts C according to Examples 1though 7 is tested and evaluated by using a tester for evaluating beltdurability shown in FIG. 6. This tester for evaluating belt durabilityincludes: large-diameter ribbed pulleys 41, 42 each having a pulleydiameter of 120 mm, one located above the other; and a small-diameterribbed pulley 43 having a pulley diameter of 45 mm, which is located tothe right of the midpoint position between the ribbed pulleys 41, 42located one above the other.

The V-ribbed belts C according to Examples 1 through 7 are each woundaround the three ribbed pulleys 41, 42 and 43 so that the ribbed part ofeach belt C makes contact therewith, tension is given to each belt C bylaterally loading a set weight of 500 N on the small-diameter ribbedpulley 43, and each belt C is allowed to run in a clockwise directionfor 1000 hours with the lower ribbed pulley 42 rotated at 4900 rpm.Then, we observed damaged condition of the back face of each belt C.

(Test and Evaluation Results)

Both test and evaluation results are shown in Table 1. Furthermore, FIG.7 shows the relationship between the angle é that the direction oforientation of the short fibers forms with respect to the belt widthwisedirection, and the belt deviation in Examples 3 through 7. TABLE 1 Beltback face reinforcement Belt deviation Longitudinal member è (°) (mm)split in belt Example 1 Back face reinforcement fabric 0 0.35 Not foundExample 2 Back face reinforcement fabric −10 0.12 Found Example 3 Shortfiber-containing rubber layer 0 0.30 Not found Example 4 Shortfiber-containing rubber layer 10 0.16 Not found Example 5 Shortfiber-containing rubber layer 20 −0.04 Not found Example 6 Shortfiber-containing rubber layer 30 −0.18 Not found Example 7 Shortfiber-containing rubber layer 40 −0.44 Not found

According to Table 1, the belt deviations in Examples 1 and 3, in whicheach belt does not have a tendency to cause side tracking in the beltwidthwise direction, are 0.35 mm and 0.30 mm, respectively. This isbelieved to be due to the fact that deviation in alignment of thetensioner pulley 23 occurs, thus exerting an action which causes beltdeviation toward the engine (i.e., toward the background of FIG. 2).

Furthermore, it can be understood that the belts according to Example 2and Examples 4 through 7, each having a tendency to cause side trackingin the belt widthwise direction, correct the belt deviation in Examples1 and 3. This is believed to be due to the fact that these belts C eachhave a tendency to run toward the direction of orientation of the shortfibers in the back face rubber layer, and thus side tracking of the beltC tends to occur when it runs, and therefore, the side tracking of thebelt C offsets the belt deviation resulting from deviation in alignmentof the tensioner pulley 23 by winding the belt C around the pulleys 21through 26 so that the side tracking of the belt C occurs in thedirection opposite to the direction in which the belt deviation occursdue to the deviation in alignment of the tensioner pulley 23.

According to FIG. 7, if the angle that the direction of orientation ofthe short fibers forms with respect to the belt widthwise direction isnot less than 0° nor more than 18°, the belt deviation becomes smallerwith an increase in this angle. On the other hand, it can be seen thatif the angle is greater than 18°, the belt deviation in the oppositedirection becomes greater with an increase in this angle. This isbelieved to be due to an inequality between the belt deviation actioncaused by deviation in alignment of the tensioner pulley 23, and theside tracking action of the belt C. That is, although the total beltdeviation appears as the sum of both the actions, if the former isgreater than the latter, the belt deviation is “+”, and if the former issmaller than the latter, the belt deviation is “−”. Therefore, if beltdeviation actions caused by deviation in alignment of the tensionerpulley 23 are substantially identical irrespective of the types of theengines, the absolute value of belt deviation can be suppressed within0.20 mm by setting the angle that the direction of orientation of theshort fibers forms with respect to the belt widthwise direction at notless than 10° nor more than 30°. Besides, by setting this angle at notless than 15° nor more than 25°, the absolute value of belt deviationcan be suppressed within about 0.10 mm.

According to Table 1, damage caused by a longitudinal split in the beltback face is observed only in Example 2. This is believed to be due tothe fact that although any direction, in which the warp and weft yarnsin the reinforcement fabric are extended, forms the same angle withrespect to the belt widthwise direction in Example 1, the direction, inwhich the bisector of the intersecting angles of the warp and weft yarnsare extended, forms an angle of −10° with respect to the belt widthwisedirection in Example 2, and therefore, the direction in which any of theyarns is extended approximately corresponds to the belt widthwisedirection so that the resistance of the belt to longitudinal splits isdegraded. It should be noted that since no damage is observed inExamples 3 through 7 in which the belt back face is reinforced with theshort fiber-containing rubber, a sufficient reinforcing effect isthought to be achieved irrespective of how the rubber is provided on thebelt back face.

Industrial Applicability

As described above, the present invention is useful to frictional forcedpower transmission belts.

1. A frictional forced power transmission belt whose back face isreinforced with a short fiber-containing rubber into which short fibersoriented in a single direction are mixed, wherein the shortfiber-containing rubber is provided integrally with the back face of thebelt so that the direction of orientation of the short fibers forms anangle with respect to the widthwise direction of the belt.
 2. Thefrictional forced power transmission belt according to claim 1, whereinthe direction of orientation of the short fibers in the shortfiber-containing rubber forms an angle of not less than 10° nor morethan 45° with respect to the widthwise direction of the belt.
 3. Thefrictional forced power transmission belt according to claim 2, whereinthe direction of orientation of the short fibers in the shortfiber-containing rubber forms an angle of not less than 10° nor morethan 30° with respect to the widthwise direction of the belt.
 4. Thefrictional forced power transmission belt according to claim 1, whereina belt body is a V-ribbed belt body.
 5. The frictional forced powertransmission belt according to claim 1, wherein the belt is used todrive accessories of an automobile.